Temporarily grounding de-energized electrical circuits may help protect personnel working on such electrical circuits. The de-energized circuits can become inadvertently energized from induced voltage from adjacent energized lines, fault-current feed-over from adjacent lines, lightning strikes anywhere on the de-energized circuit, switching-equipment malfunction or human error, and accident-initiated contact with adjacent lines. Since any one of the above could result in re-energizing the de-energized electrical circuit, utilities may treat these potential dangers as ever-present and impose temporary-grounding work rules.
There are a number of types of ground clamps available, e.g. C-type grounding clamps, bus bar grounding clamps, snap-on or duckbill-type grounding clamps, and all-angle grounding clamps. All-angle grounding clamps can clamp to an electric line at many different angles providing greater flexability than other types of ground clamps. For high voltage and high current scenarios, clamps require low resistance to ensure proper grounding in the event of a short circuit fault. Since all-angle temporary ground clamps may rely on multiple components assembled in a manner that allows multiple degrees of freedom, each connection point may increase resistance.
For these and/or other considerations, all-angle temporary ground clamps may not be capable of withstanding fault currents at an ASTM Grade 5H level (Rated Current 47 kA with High Asymmetrical Requirement X/R=30 for 15 cycles, wherein the X/R is the ratio of reactance to resistance of the electrical impedance of a faulted (short) circuit from the source of fault current to the location of the fault on the circuit). Accordingly, an all-angle temporary ground clamp capable of withstanding fault currents at an ASTM Grade 5H level or higher may be desired in the field.